Rotary presses have been developed for punching holes in webs or rolls of paper, cardboard or similar material. Such presses generally include a pair of counter-rotating rings which are positioned such that a strip of paper, cardboard or similar material may be fed between them. One ring carries a plurality of punches which extend radially outwardly from the ring. The periphery of the other ring is provided with a plurality of dies which are sized and spaced apart such that the punches register with and enter respective dies to thereby punch holes in the material being fed between the rings.
In general, the punches are made from a relatively soft steel, while the dies are made from a hardened steel. Thus, if the punches are out of alignment with the dies, the punches can be prematurely worn out. Also, the inherent abrasiveness of the material being fed between the rings causes the punches to be worn out even if they are properly aligned with the dies. Sometimes, only a single punch must be replaced. Other times, an entire set of punch elements must be replaced.
In a vast majority of the prior art rotary presses, the punch rings are made from a pair of half rings which are directly attached to a shaft of the press for rotation therewith. The punches can be replaced individually (see U.S. Pat. No. 3,828,632) or in pairs (see U.S. Pat. No. 3,106,859). Inasmuch as each half ring typically carries as many as twenty-eight or more punches, it is extremely time consuming to change an entire set of punches, regardless of whether they are replaced individually or in pairs. The longer that it takes to replace the punches the longer that the press will be inoperable and therefore unproductive.
At least one known punch ring includes a collar and punch ring segments removably attached to the collar. The punch ring segments are, however, not interchangeable or replaceable with new pre-loaded segments. Thus, like in the other prior art punch rings, the punches cannot be removed and replaced in groups greater than two. Accordingly, it would still be a time-consuming procedure to replace an entire set of punches.